Bacterial Meningitis

1) Clinical Presentation of Bacterial Meningitis

• Classic triad of symptoms: Fever, Nuchal Rigidity, and Altered mental status - all 3 are rarely seen, but rare to have meningitis in the absence of at least one of those symptoms.
• Other symptoms include headache, photophobia, nausea/vomiting, neurological symptoms (seizures, focal deficits, hydrocephalus), and possibly petechial rash/purpura with meningococcal meningitis.
• On exam, remember that Brudzinski's sign and Kernig's sign are highly insensitive, but actually quite specific (~95%) - so arguably they are worth doing: if negative, not helpful, but if positive, be much more concerned!  Nuchal rigidity is not particularly sensitive or specific.  Jolt accentuation test, whereby the patient horizontally moves head rapidly causing increased headache, is actually fairly sensitive > specific.

 

 

2) Microbiology of Bacterial Meningitis

Community-Acquired:

• Strep pneumo = most common
• Neisseria meningitides
• H.influenza
• Listeria.  Risk factors for Listeria = Age > 50, immunocompromised state, pregnancy, alcoholics

Healthcare-Associated: i.e. neurosurgery, VP shunts or EVDs, epidural procedures – worry about Staph (coag negative and S.aureus) and gram negatives including Pseudomonas

 

 

3) Indications for CT scan before LP – 2004 IDSA Guidelines

Main concern is unrecognized increased ICP, whereby LP leads to cerebral herniation and death.

1. Immunocompromised state – higher risk of mass lesions including abscesses and malignancy
2. Focal neurological deficits
3. History of CNS disease – mass lesion, major CVA
4. New onset Seizures within 1 week of presentation
5. Papilledema on exam
6. Abnormally decreased mental status – partially because you cannot do a neuro exam

Seriously consider memorizing these criteria, because it turns out most patients do NOT need a CT scan prior to LP, and this just leads to needless delay in diagnosis and treatment.

Note that our patient actually met 2 criteria for CT scan - her mental status and her focal neurological deficit (with her left facial droop).  Do not forget these indications for CT scan prior to LP otherwise you will look bad like the OSH doctors.

 

 

4) Management of Bacterial Meningitis
General principle is that you need to start appropriate antibiotics ASAP.   If LP is going to be delayed by need for CT scan, obtain blood cultures and start Abxs right away.

Empiric therapy:

• Vancomycin --> for PCN-resistant S.pneumo, NOT for MRSA (unless you are worried about health-care associated meningitis)

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• Ceftriaxone – 2 g q12 hours – note the higher dosing (usually 1-2 g q24 hrs) -->for non-resistant S.pneumo, N.meningitidis, and H.influenza.  Do not forget to use the correct Ceftriaxone dosing otherwise you will look bad like the OSH doctors.

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• (Ampicillin – for all pts > 50 yo, immunocompromised, pregnant)

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• Dexamethasone 10 mg IV q6 hrs – per 2004 IDSA guidelines, start for all pts with suspected bacterial meningitis immediately prior to or with first dose of Abxs.  Basic idea is to decrease CNS inflammation which is worsened by Abx-mediated killing of bacteria (similar to rationale for steroids for severe PCP pneumonia).   Benefit is only definitively seen for S.pneumo meningitis, guidelines recommend to stop steroids if other bug is isolated (although this is somewhat controversial).  

 

(Chanu Rhee MD, 10/11/10)